I. Cross-Reference to Related Application
This application is a 371 of International application no. PCT/US2010/050501, filed Sep. 28, 2010, and claims priority from that application which is also deemed incorporated by reference in its entirety in this application
II. Field of the Invention
The present invention relates generally to vehicle-mounted roof racks for transporting loads, and more particularly to a movable ladder rack that can be used to readily load a ladder onto the roof area of a truck or van and to lower it from the roof area to a position allowing the ladder to be manually carried away to a worksite.
III. Discussion of the Prior Art
In my earlier U.S. Pat. Nos. 5,297,912; 6,092,972; 6,099,231; and 6,427,889, the teachings of which are hereby incorporated by reference, there are described different designs of truck or van-mounted ladder racks that facilitate the loading and unloading of one or more ladders with respect to the vehicle's roof. These devices comprise front and rear four-bar linkage assemblies that include a stationary member which is adapted to rigidly affixed to the vehicle's roof or to cross-members that clamp to the vehicle's roof, and a ladder support member pivotally joined to the stationary member by a pair of transversely spaced links. A drive shaft is journaled for rotation in the stationary members of the front and rear four-bar linkage assemblies and is rigidly affixed to one of the pair of links of the front and rear four-bar linkage assemblies. Thus, when the drive shaft is rotated, either manually with a crank or automatically by means of a motor, ladders resting on the front and rear ladder support members are lifted and rotated from a position parallel to the vehicle's roof to a position parallel to the vehicle's side during an unloading maneuver. When reloading ladders onto the vehicle, the drive shaft is rotated in an opposite direction to raise and rotate the ladder load onto the vehicle's roof.
In my earlier designs described in the aforereferenced patents, the four-bar linkages have been designed such that the top and foot of the ladders remain generally horizontal throughout their range of motion as the drive shaft is rotated.
While the earlier designs reflected in the above-listed patents greatly simplify the loading and unloading of heavy extension ladders onto and from transport vehicles, it is deemed advantageous to provide a rotatable ladder rack assembly for a motor vehicle that requires less force to be applied during the unloading and reloading operations. My U.S. Pat. No. 6,764,268 describes a ladder rack arrangement in which the frontmost four-bar linkage assembly allows a ladder to be transferred from the vehicle's roof to a position alongside the vehicle where the upper end of the ladder is at a raised elevation relative to the ladder's foot such that the ladder is inclined relative to the horizontal. The height drop from the rooftop position to its lowered disposition is reduced such that less force is required to operate the ladder rack. Furthermore, with the inclined position, the ladder feet are lowered further such that a workman is better able to grasp the ladder at its foot end while the top or front end of the ladder is still engaged and supported by the front ladder support member. This permits the foot of the ladder to be lifted free of the rear ladder support member and lowered to the ground with the top end of the ladder still being supported by the front ladder support member. This also reduces the manual effort and ultimately standing the ladder vertically.
With the arrangement described in the aforereferenced U.S. Pat. No. 6,764,268, the contents of which are hereby incorporated by reference, it is still necessary for the user to manually lift the front end of the ladder to loop its upper rail onto the hook arm 41 followed by the step of lifting the rear end of the ladder so that its upper rail is cradled by the hook arm 19 on the rear four-bar linkage assembly. This has proved to be somewhat challenging for users having limited upper body strength.
It is a purpose of the present invention to provide a movable ladder rack assembly that eliminates the foregoing drawback of the ladder rack described in my '268 patent.